With users' higher and higher requirements for wireless access rate, Wireless Local Area Network (WLAN) emerges as the times require, which can provide high-rate wireless data access in a small area. WLAN incorporates various techniques, among which a widely applied technical standard is IEEE 802.11b, which adopts 2.4 GHz frequency band and the highest data transmission rate thereof can be as high as 11 Mbps. IEEE 802.11g and Bluetooth technology also adopt this frequency band and the highest data transmission rate of 802.11g can be as high as 54 Mbps. Other new standards like IEEE 802.11a and ETSI BRAN Hiperlan2 adopt 5 GHz frequency band, and the highest transmission rate can also be as high as 54 Mbps.
Although there are various wireless access techniques, most WLAN are used to transmit Internet Protocol (IP) data packet. As for a wireless IP network, the specific WLAN access technique adopted is transparent to upper hierarchy IP. Users access a wireless IP network through Access Points (AP), and the network control and connection devices are connected to constitute an IP transmission network.
With the rising and development of WLAN technology, intercommunication between WLAN and various wireless mobile communication networks becomes the current research focus, wherein the wireless mobile communication network can be Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA) system, Wideband Code Division Multiple Access (WCDMA) system, Time Division-Synchronous Code Division Multiple Access (TO-SCDMA) system and CDMA2000 system. With the Third Generation Partnership Project (3GPP) standards, a user terminal can be connected to the Internet or Intranet through WLAN access network, or be connected to home network of 3GPP system or visited network of 3GPP system through WLAN access network. Specifically speaking, when getting accessed locally, a WLAN user terminal is connected to 3GPP home network through a WLAN access network; when roaming, the WLAN user terminal is connected to 3GPP visited network through a WLAN access network. Some of the entities in 3GPP visited network are interconnected with corresponding entities which have the same functions in 3GPP home network, for instance, 3GPP Authentication Authorization and Accounting (AAA) Proxy in 3GPP visited network and 3GPP Authentication Authorization and Accounting (AAA) Server in 3GPP home network; WLAN Access Gateway (WAG) in 3GPP visited network and Packet Data Gateway (PDG) in 3GPP home network, and so on, as shown in FIG. 1.
As shown in FIG. 1, 3GPP system is mainly composed of Home Subscriber Server (HSS)/Home Location Register (HLR), 3GPP AAA Server, 3GPP AAA Proxy, WAG, Packet Data Gateway, Offline Charging System and Online Charging System (OCS). WLAN user terminal (WLAN UE), WLAN access network and all entities of 3GPP system constitute a 3GPP-WLAN interworking network, and this 3GPP-WLAN interworking network can be taken as a WLAN service system. 3GPP AAA Server takes charge of authentication, authorization and accounting of the user, as well as collecting the charging information transmitted by WLAN access network and transmitting the collected information to charging system. Packet Data Gateway takes charge of transmitting user data from WLAN access network to 3GPP network or to other packet networks. Charging system mainly receives and records the user's charging information transmitted from the network. OCS system guides the network to transmit online charging information periodically according to the expenses of an online charged user, and makes appropriate statistics and control operations.
In normal conditions, when a WLAN user terminal desires to access a 3GPP-WLAN network, this user terminal will send an access request to corresponding access authentication unit in 3GPP-WLAN network through WLAN access network; the access authentication unit, which is usually a 3GPP AAA Server, authenticates the request after receiving it. If the request passes the authentication, all ports will simply be opened to this user terminal. However, the structure of an operational WLAN is much more complicated than the simplified network structure shown in FIG. 1. Here, said operational WLAN refers to a WLAN that can be operated and managed, which will not only perform authentication, authorization and accounting of a user, but also provide one or more than one kind of network access and network-based service, for example, various local area network (LAN) services like LAN inside local hotels or airports and LAN games, as well as access to a LAN that can provide different services, Internet access and services based on 3GPP packet network.
Because an operational WLAN can access to different LANs at the same time and the operational rules are comparatively complicated, different access rules may be set according to the users account and accessing time. Therefore, the traditional method of access authorization based only on the authentication result is incontrollable and inconvenient for operation.